Perhaps you think I must be some uberathlete who can waltz up mountains like a cakewalk.
Not exactly. When I was young(er) I was a gymnast, and did quite a bit of rock climbing and some mountaineering, including multiple ascents of Devil's Tower and reached the top of Mount Rainier in high school (14, 410 feet).
When I was in college I developed an inflammatory arthritis (psoriatic arthritis; yes, young people do develop arthritis as many of you know from personal experience). This put the kabosh on highly pounding activities for a number of years since inflammation in psoriatic arthritis is pretty use-dependent. I turned to swimming from running to stay in shape (swimming is great exercise and very joint friendly; if you have joint issues and haven't tried swimming, give it a go)! Subsequently my trusty rheumatologist, whose goal is to keep me able to do as many of the active things I like to do as possible, recommended a tumor necrosis factor alpha blocker. I have had my ups and downs with that, but when things are going well, I can once again push myself pretty hard without disastrous joint flares. Better living through chemistry! Living with a chronic disease isn't always easy, but with good medical care, keeping a positive attitude, and controlling the things that are within my control, I have once again been able to do a lot of things I had pretty much accepted as forever in my past.
All of this I mention just to let you know that I too have my own limitations and obstacles, and know a bit what it is like to wonder how one's health is going to behave. Kilimanjaro is going to be a serious workout for my body, but 80% of climbing a mountain is attitude and perseverance.
Three months to go; I am looking forward every day!